Rats are nice too!

http://www.nytimes.com/2011/12/13/science/observatory-rats-have-empathy-study-finds.html?ref=science

A new study in the journal "Science," rats were shown to release trapped companions, even it would benefit them in no way. When rats were given the choice to release a companion into a separate cage where they wouldn't be able to interact with them, the rats did so. Even when given the choice between chocolate and releasing their comrades, the rats favored their companion's freedom.